Hand-held fastener driving tools have been available for use with collated strips of fasteners, such as screws. Some conventional collated strip screw driving tools have a front or nose portion that is permanently attached to the main body of the tool, and this nose portion is pressed against a surface that the fastener will be driven into. The nose portion has an indexing mechanism to index the position of the collated strip to the next screw that will be driven. Such tools typically have a depth of drive user adjustment, to control how far the fastener or screw will be driven into the solid object by the tool.
Other types of conventional fastener driving tools use an attachment that is placed over a portable electrical tool, such as a drill or a screw driving tool, and this attachment allows the other portable tool to be used with a collated strip of screws (or other type of fasteners). The conventional attachment includes a movable nose piece that is pressed against the solid surface, and typically would have some type of depth of drive user control.
In the conventional self-contained screw driving tools, the entire nose portion is not easily detached from the main body of the tool, and an example of such a construction is disclosed in U.S. Pat. No. 5,988,026, co-assigned to Senco Products, Inc. of Cincinnati, Ohio. A detachable nose portion may have certain advantages, and a torque limiting control circuit could be used in place of a depth of drive control for such a configuration.
In some conventional self-contained screw driving tools (both single-feed and automatic-feed with a collated strip), a maximum torque control is provided, but it is a mechanical device that disengages a clutch or uses another type of mechanical drive component (e.g., a ratchet), and it does not shut off the electric motor. Therefore, a user could continue to “drive” the fastener (to make sure that it is really bottomed) and drain the tool's battery power source, by spinning the motor even though the mechanical drive is essentially not further tightening the fastener. Moreover, such a ratchet tends to make considerable acoustic noise when this occurs. Finally, most mechanical torque control devices are not all that repeatable in limiting the maximum torque applied to the fastener.